The present disclosure relates to an image sensor and an electronic device, and more particularly to an image sensor and electronic device that can reduce noise generation.
Recently, complementary metal-oxide-semiconductor (CMOS) image sensors are widely used as imaging devices. In general, however, pixels in the CMOS image sensor are sequentially read one at a time, so it is difficult to obtain simultaneity for an entire image.
That is, in the CMOS image sensor, photocharges created by a photoelectric converting unit and stored therein are sequentially scanned and read one pixel or one line of pixels at a time. When this sequential scanning is performed, that is, a rolling shutter is used as an electronic shutter, it is difficult to start an exposure, during which photocharges are stored, for all pixels at the same time and to terminate the disclosure for all pixels at the same time. Accordingly, sequential scanning is problematic in that a captured image of a moving subject is distorted.
In sensing applications in which this type of image distortion is not allowed, such as when a subject moving at high speed is captured or simultaneity is desirable for a captured image, a global shutter is used that starts an exposure for all pixels in a pixel array at the same time and terminates the exposure for all pixels at the same time.
An image sensor that uses a global shutter as an electronic shutter includes a charge storage unit formed with, for example, a semiconductor memory in each pixel. In this type of image sensor, charges are simultaneously transferred from a photodiode to the semiconductor memory and are stored therein, after which the stored charges are sequentially read to obtain simultaneity for an entire image (see Japanese Unexamined Patent Application Publication No. 2008-103647, for example).